星系团, 星云团

скопление внегалактических туманностей, скопление галактик

星云星际空间的尘埃或气体或两者共同构成的巨大天体，由其对光线的吸收和反射来决定其明亮可见或黑暗一团

A diffuse mass of interstellar dust or gas or both, visible as luminous patches or areas of darkness depending on the way the mass absorbs or reflects incident radiation.